Abstract Gliomas account for about 60% of all primary CNS tumors. Glioblastoma (GBM) or grade IV gliomas which comprise 50.9% of all gliomas are the most malignant form. Glioblastoma tumors are highly heterogeneous and there is a complex interaction among different types of tumor cells and stromal cells within the tumor. Recently it has been shown that the majority of tumor cells do not have the capacity to recapitulate a phenocopy of the original tumor and that only a small subpopulation of cells in the tumor, called cancer stem cells, have that ability upon xenotransplantation in nude mice. These cancer stem cells appear to be more resistant to conventional therapy, like chemotherapy and radiation, as compared to the non-cancer stem cells. Following current therapy for high-grade glioma tumors, most patients die within a year from a new secondary tumor foci forming within one centimeter of the resected area. These foci are enriched for cancer stem cells, and it is likely that they are responsible for tumor recurrence. Our proposal focuses on identifying small molecule drugs which can increase therapeutic efficacy for GBM stem cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a potential anti-cancer agent. However, a considerable number of different types of cancer cells, including GBM, are resistant to apoptosis induction by TRAIL. We plan to identity drug candidates which either kill primary GBM stem cells directly or can sensitize these cells to TRAIL-induced apoptosis. We will use a high throughput apoptosis-screening assay which we have developed based on the naturally secreted Gaussia luciferase and screen different small molecule libraries including ones containing FDA-approved drugs which crosses the blood-brain barrier. We will validate the most promising drug hits in our experimental glioma stem cells-bioluminescent model in vivo.